Chemical metabolism and toxicity to early life stages of fish

烷基多环芳烃（PAH）存在于原油、杂酚油以及河流和港口的污染沉积物中。 烷基PAH根据其母体结构和侧链中的碳数进行分类。有十几个类别，而一个类别，如烷基菲，可能包括500多个独特的化合物与1至4个碳的侧链。虽然研究很少，但它们占原油中多环芳烃总量的90%以上，并对埃克森巴尔德斯石油泄漏对渔业的影响做出了贡献。它们迅速被鱼类吸收，鱼类通过产生细胞色素P450（CYP1A）酶作出反应。 这些酶将氧添加到烷基PAH中作为其排泄的第一步。 然而，氧合可能产生比母体化合物更有害的代谢物。 因此，更快的排泄带来更大的毒性风险，表现为循环衰竭和胚胎和幼虫死亡，这是最敏感的生命阶段。

Alkyl polycyclic aromatic hydrocarbons (PAH with one or more alkyl side chains) are found in crude oil, creosote, and contaminated sediments of rivers and harbours. Alkyl PAH are classified according to their parent structures and to the numbers of carbons in side chains. There are more than a dozen classes, and a single class, such as alkyl phenanthrenes, may include more than 500 unique compounds with 1 to 4 carbons in side chains. While little studied, they comprise more than 90% of total PAH in crude oil, and contributed to the impacts on fisheries of the Exxon Valdez oil spill. They are rapidly taken up by fish, which respond by producing cytochrome-P450 (CYP1A) enzymes. These enzymes add oxygen to alkyl PAH as the first step in their excretion. However, oxygenation may create metabolites that are more harmful than the parent compound. Hence, faster excretion carries a risk of greater toxicity, which is expressed as circulatory collapse and death of embryos and larvae, the most sensitive life stages.